MISSION 29P

Preface

A YouTube video of a BAA Webinar on the subject of this most unusual solar system object has been available since 2021 May 14. It features Prof Laura Woodney of California State University, San Bernardino and myself presenting some latest findings about this object and talking about possibilities of sending a space probe to investigate further.

Coverage of the latest apparition of 29P began with observations by Jean-François Soulier during the early hours of June 25.

What is Comet 29P?

This comet (aka 29P/Schwassmann-Wachmann 1) is the most observable that exists and yet we understand very little about it. It is the second-most active body in our Solar System, after Jupiter's moon, Io, in that its level of volcanism is engendered by tidal interactions with the planet. The Comet Section has therefore launched this special project to ensure that our understanding of it is much improved such that it becomes the most observed comet that we know of.

This mysterious object is temporarily locked in its present near-circular orbit by the gravity of the giant planets, Jupiter and Saturn. Located at a mean heliocentric distance of 6.0 au, 29P describes an orbit around the Sun every 14.7 years or so, with a perihelion distance of 5.7 au and aphelion of 6.3 au. Because it never approaches the Sun closely, it never exhibits a distinctive tail, i.e. quite unlike most people’s idea of a comet. But like Jupiter and Saturn, the comet is observable during most of each year apart from the couple of months it spends in solar conjunction. Current location in the JPL Small-Body Database Browser.

Intensive observations have been underway since 2014 when the mini-outburst phenomenon was discovered, i.e. weak outbursts not exceeeding 1.0 mag in amplitude. The following set of plots show its behaviour during its seven 2014-2020 apparitions (click on the image to obtain larger views). The provisional plot for 2020 has been included.

So what can you do as an observer?

First if you want to capture images that can be used to perform photometry then do consult the Observing Tutorial.

Currently Richard Miles coordinates the observing campaign so please direct any queries to him. The main objectives are:

1. Detect any new outburst as soon as possible after it has taken place so that we can (a) determine the time of the event, and (b) initiate 'target of opportunity' images with the 2.0-m Faulkes Telescopes to study the resulting expanding coma.

2. Measure the brightness of the inner coma and determine (a) the maximum brightness of each outburst, and (b) follow its subsequent decline photometrically.

3. Establish a long-term archive of: (a) its photometric lightcurve (intensive observations began in 2014); (b) a high-precision astrometry archive (so its orbit is precisely known for the prediction of stellar occultations); and (c) archive images series depicting the development of the expanding coma after each significant outburst

By recording its characteristics in this way it is hoped that we can elucidate the true nature of this object

 

Current Status and Latest Observations:

The 2021-apparition is now over with a record 338.5 days of coverage, the longest such coverage of any apparition and also the most observing epochs achieved (1168). The observers who contributed were:

The following image is the last one taken this apparition with the comet at only 19° solar elongation. It is not detected which means it was fainter than magnitude 16.0R at that time.

29P appears to have had a mini-outburst of 0.9 mag amplitude whilst at 25° solar elongation. Here's the image:

Patrick Wiggins observing from Utah has confirmed the mini-outburst, his observations yielding a magnitude of 15.74R.

Two very weak mini-outbursts occurred during March. They both were of just 0.11 magnitudes amplitude reaching 16.9R:

With many dedicated observers following 29P, we get a much more reliable evaluation of small brightness changes even though it is now 17th magnitude. This is a good demonstration of the benefit of having more observers. For the first 11 days of coverage, the intrinsic trend due to varying distance and phase angle is expected to be a fade of 0.018 mag. However on March 17.46 +/-0.28 there looks to have been a step-change of 0.11 mag (red datapoints). This is the smallest mini-outburst that we have detected.

Recent images:

The following two images were taken at almost the same time. The one on the right is unfiltered. You can see extra coma further from the nucleus than can be seen in the r'-filtered image on the left. The reason for this may be that the nucleus has been almost quiescent during the past 30 days with little debris ejected far into space since most of it falls back. So what does escape is gas from sublimating hypervolatile ices and it is the emission lines from the gas that adds to the coma brightness far from the nucleus.

We know that the main gas species is carbon monoxide and most CO+ emission lines appear at wavelengths shorter than the passband of the r' filter (550-690 nm). Also nitrogen (N2+) emission is mostly at the blue end of the spectrum Unfiltered images should pick up these faint gaseous emissions as can be seen in Jean-François Soulier's image on the right.

See plot below also showing how data from several observers monitoring the comet allows us to detect small outbursts. We've had a couple of such events in the last two weeks or so as shown in these plots:

 

Thanks to Jean-François Soulier (L27, Haute-Provence, France) and Nick James (970, Chelmsford, UK) who independently discovered the comet going into outburst. Thanks to Nick's timely alert we have obtained the best coverage ever of one of this comet's outbursts. Here is a plot of the data from L27 showing the outburst lightcurve analysed in terms of the G magnitude using a 10" radius photometric aperture. A video of this outburst has been prepared by Jean-François.

Another outburst also took place less than 6 days later on 2020 November 25.45±0.24 with the magnitude going from 15.3R to 14.3R

29P reached opposition on November 6 and so now appears in the early evening sky making it an excellent target for northern hemisphere observers. Located in Aries at a declination of +24 degrees, the comet is visible for a couple of hours after sunset between now and the end of April.

Here below is the final light-curve for 2020-2021 showing its activity during this apparition up to April 24. Click on the plot if you want to see the full-size image. There have been two very strong outbursts: one on July 26 and a second on November 19, minute-by-minute coverage of which we have achieved largely thanks to Jean-François Soulier's dedicated 29PREMOTE observatory. More on those findings later. Jean-François was also successful in catching the start of the August 22 event. In all we now have outburst lightcurves spanning the first few critical hours for FOUR events namely in 2017, 2019 and 2020(2).

In addition to strong outbursts, the nucleus has exhibited at least 24 mini-outbursts some of which have been so weak that there have been 5 instances where a large fraction of the ejecta have, after several days, fallen back onto the nucleus. This happens because the nucleus is very large (approx. 64 km across) and so has a relatively high gravity and high escape velocity (approx. 20-25 m/s). Our detailed observations are revealing this collapse of the inner coma - a behaviour unique to this body! We might indeed consider 29P not to be a comet but instead a unique Transition Object that was once a TNO.

Observational data in MPC format

Full archive datasets 

List of Observers:

List of Observatory Codes / Observers / Instruments / Photometric aperture in arcsec

N.B. This is a comprehensive list of observatories/people whose work has contributed to the current Observing Campaign, which began in 2014 February.

203 G. Galli, S. Foglia Italy 0.36-m f/5.76 Schmidt-Cassegrain 5.5
204 L. Buzzi, A. Aletti Italy 0.36-m f/6.5 reflector 4.8/6.0; Italy 0.84-m f/3.5 reflector 5.6 
213 R. Naves, M. Campas Spain 0.30-m f/10 Schmidt-Cassegrain 10.0 square; Spain 0.30-m f/9 Schmidt-Cassegrain 5.4
323 P. Camilleri, J. Oey, R. Miles Australia 0.40-m f/5 reflector (Perth)
718 P. Wiggins Utah, USA 0.35-m f/7 Schmidt-Cassegrain 5.2
970 N. James England 0.28-m f/10 Schmidt-Cassegrain 5.2/5.8 check
A06 E. Cortes Spain 0.25-m f/3.6 Schmidt-Cassegrain 10.0 square
A77 J.-F. Soulier, F. Kugel France 0.20-m f/4 Newtonian reflector 5.0/6.6
B74 J. M. Bosch Spain 0.40-m f/10 Schmidt-Cassegrain 10.0 square
B96 E. Bryssinck Belgium 0.4-m f/3.8 astrograph 5.0
C10 J.-F. Soulier France 0.30-m f/3.8 Newtonian reflector 6.5, 4.9
C35 J. Aledo Spain 0.4-m f/3.4 Reflector 10.0 square

C42 Q. Ye (Zwicky Transient Facility) Xingming, China 0.50-m ?

C77 A. Mantero Italy 0.25-m f/4 Reflector 6.7
C90 L. Tremosa Spain 0.30-m f/5 reflector 10.0 square
E94 J. Drummond N.Zealand 0.35-m f/10 Schmidt-Cassegrain 5.9; 0.41-m f/5.2 Newtonian 7.2; 0.41-m f/4.5 Newtonian 6.0
G40 J. Tuten Canary Isles 0.43-m f/6.8 Dall-Kirkham 5.0
H06 N. James New Mexico 0.43-m f/4.5 5.8; A. Watkins New Mexico 0.43-m f/4.5 5.8
I41 Q. Ye (Zwicky Transient Facility) Palomar, USA 1.20-m f/2.5
I64 A. Jones England 0.19-m f/5.2 Mak-Newt + Rc filter 5.6
I81 D. Buczynski Scotland 0.35-m f/6 Schmidt-Cassegrain 5.2
I88 J. Carrillo Spain 0.36-m f/5 reflector 10.0 square
J01 J. Gonzalez Spain 0.15-m f/6 Ritchey-Chretien 10.0 square
J22 K. Hills La Palma 0.50-m f/2.9 astrograph 5.9, 10.0 square
J24 J. F. Hernandez Spain 0.4-m f/10 Schmidt-Cassegrain 10.0 square
J38 F. Garcia Spain 0.25-m f/8.1 Ritchey-Chretien 10.0 square
J47 G. Muler Lanzarote 0.30-m Schmdt-Cassegrain 6.1
J77 R. Miles England 0.35-m f/8 Schmidt-Cassegrain + r' 5.4 also V, B, Clear
K01 A. Watkins England 0.35-m f/7.7 Schmidt-Cassegrain 6.2
K02 P. Carson England 0.32-m f/5.4 Dall-Kirkham 5.5/6.5
K14 M. Morales Spain 0.25-m f/5 Newtonian 5.7, 10.0 square
L27 J.-F. Soulier France 0.20-m f/4 Newtonian reflector 6.5, 5.0
Q38 M. Mattiazzo Australia 0.28-m f/6.3 Schmidt-Cassegrain 5.5
Q67 P. Camilleri, J. Oey, R. Miles Australia 0.32-m F/8.8 RCOS 5.5
Q68 P. Camilleri, J. Oey, H. Williams Australia 0.30-m f/3.0 reflector 7.4; P. Camilleri, J. Oey Australia 0.34-m f/5.9 SCT
W88 K. Breedlove, J. Tuten, A. Hale Chile 0.35-m f/11 Schmidt-Cassegrain (Slooh) ???
W96 J.-F.Soulier, A.Maury, J.-B. de Vanssay Chile 0.4-m f/5.2 Ritchey-Chretien 6.4
Z08 E. Bryssinck Oria, Spain 0.70-m f/6 reflector (remote) 5.2 r'

Z10 P. Carson Spain 0.32-m f/5.4 Dall-Kirkham 5.5
Z30 D. Storey England 0.35-m Ritchey-Chretien 5.9
Z39 A. Acosta Lanzarote 0.23-m Schmidt-Cassegrain 10.0 square
Z42 J. Savage England 0.35-m f/7.7 Schmidt-Cassegrain + V 5.5, 7.9
Z74 F. Soldan Spain 0.20-m f/6.7 Schmidt-Cassegrain 10.0 square
Z80 G. Wells, D. Bamberger England 0.25-m f/8 Ritchey-Chretien 6.7
Z85 T. Angel Spain 0.35-m f/11 Schmidt-Cassegrain 5.6
XXX C.S. Morris California, USA 0.406-m f/6.8 Schmidt-Cassegrain 4.84

Las Cumbres Observatory / Faulkes Telescope Project (R. Miles, A. Hale):

A major contribution to this '24/7' comet monitoring activity have been the observations from the Las Cumbres Observatoryglobal network of telescopes. Access to this network has been made available thanks to the Dill Faulkes Education Trust, and to Dr Paul Roche of the Faulkes Telescope Project based at Cardiff University, Wales assisted by Alison Tripp.  

E10 coj 2m0a Siding Spring-FT South 2.0-m f/10 Ritchey-Chretien 5.4
F65 ogg 2m0a Haleakala-FT North 2.0-m f/10 Ritchey-Chretien 5.4

K91 cpt Sutherland A S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K92 cpt Sutherland B S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K93 cpt Sutherland C S. Africa 1.0-m f/8 Ritchey-Chretien 5.5

Q63 coj Siding Spring A Australia 1.0-m f/8 Ritchey-Chretien 5.5

Q64 coj Siding Spring B Australia 1.0-m f/8 Ritchey-Chretien 5.5
V37 elp McDonald Observatory A Texas, USA

Latest rotational phase plot showing all outbursts since 2002 August: